Methylene disulfonate compounds are usable as pharmaceutical preparations for treating leukemia in animals, etc. Known methods for producing a methylene disulfonate compound include the following.
(1) A method wherein sulfonyl chloride is reacted with silver carbonate, and the resulting silver sulfonate is reacted with diiodomethane (WO85/03075);

(2) A method wherein alkanedisulfonic acid is reacted with methylene diacetate (JP 2005-336155 A).

However, these methods have various drawbacks. For example, the silver carbonate and diiodomethane used in the method of (1) are expensive and the reaction is slow. The method of (2) uses methylene diacetate, which is not easily obtainable and expensive.